The most prevalent infections in the oral cavity are represented by periodontal diseases and candidal infections. Both result in an immune response represented, in part, by innate mechanisms. Antibiotic peptides are considered a key component of innate immunity. The beta-defensins are recently discovered antimicrobial peptides produced by epithelial cells whose role in protection against oral infections is as yet unknown. The hypothesis underlying the planned research is that beta-defensins function as antimicrobial agents in periodontal diseases and Candida infections. In this application, the Principal Investigator proposes studies of human beta-defensins 1 and 2 (HBD1 and 2) which they and others have recently found to be expressed in oral epithelia. The following specific aims are proposed for these studies. Aim 1 is to determine the cell-specific localization and expression of HBD-1 and HBD-2 in the oral cavity in health and disease. This aim will be addressed using both in situ hybridization and immunohistochemistry to reveal localization, and ribonuclease protection assays and RT-PCR to indicate expression. Secretion of the peptides will be assessed using Western blots. Aim 2 is to determine what the antimicrobial properties of the human beta-defensins are against periodontal bacteria and Candida. Using recombinant peptides in established antimicrobial assays, the spectrum of antimicrobial activity of the beta-defensins against oral organisms will be determined. Aim 3 is to determine what factors regulate the expression and secretion of beta-defensins in oral epithelia. To understand how beta-defensin gene expression and secretion may be regulated, cultured oral keratinocytes will be treated with candidate regulatory factors including periodontal bacteria, Candida organisms, pro- and anti-inflammatory cytokines and glucocorticoids. Expression of mRNA and peptide levels will be examined through the use of ribonuclease protection assays and Western blots, respectively. From these studies the Principal Investigator hopes to increase current understanding of the role beta-defensins play in the innate immunity of periodontal and Candida infections so as to be able to develop new therapeutic modalities against a group of prevalent oral diseases.